HHE Report No. HETA-93-1134-2400, Sterling Van
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AdditionalAdditional HHEHHE reporreporttss areare avaavaililabablele atat hhtttpp::///wwwwww..ccddcc..govgov//nnioiosshh//hhehhe//reporreporttss This Health Hazard Evaluation (HHE) report and any recommendations made herein are for the specific facility evaluated and may not be universally applicable. Any recommendations made are not to be considered as final statements of NIOSH policy or of any agency or individual involved. Additional HHE reports are available at http://www.cdc.gov/niosh/hhe/reports HETA 93-1134-2400 NIOSH INVESTIGATOR: JANUARY 1994 MATTHEW KLEIN, P.E. STERLING VAN DYKE CREDIT UNION STERLING HEIGHTS, MICHIGAN I. SUMMARY On September 24, 1993, the National Institute for Occupational Safety and Health (NIOSH) received a confidential request for a health hazard evaluation (HHE) at the Sterling Van Dyke Credit Union in Sterling Heights, Michigan from employees of the credit union. These employees were concerned about recurring illnesses. Symptoms and illnesses reported by the employees included headaches, backaches, breathing difficulty, purple fingernail beds, disrupted menstrual cycles, asthma, and bronchitis. One requester also reported that at least four employees were using bronchial dilator inhalers. At least one of these employees was confirmed to have asthma by a pulmonologist; the others were thought to have, but not confirmed to have, asthma. A survey was conducted at the credit union on October 20 through 22, 1993. On October 20, inspections were made of the heating, ventilating, and air conditioning (HVAC) system that served the building, and symptom questionnaires were distributed to all employees. On October 21, dry bulb temperature, relative humidity, and carbon dioxide (CO2) measurements were made. Measurements were made at 9 locations in the building and one location outside of the building. Four sets of measurements were made inside the building and three sets outside the building. Measurements were made in the morning as employees were arriving, late morning, early afternoon, and late afternoon as employees were leaving. A closing meeting was held on October 22. Questionnaire results of symptoms could only show possible, not definite, links to other survey findings. For example, 64% of the questionnaire respondents reported cough symptoms, and 57% reported tired or strained eyes and sore or dry throats on the day the questionnaire was completed. Given the design and operation of the ventilation systems, and the facts that smoking is allowed in the building and that over 50% of the employees smoke, exposure to environmental tobacco smoke (ETS) is a likely contributor to some of the symptoms. Questionnaire results about workplace conditions could be better explained by other findings made during the survey of the building. For example, 79% of respondents felt that the building had too little air movement on the day of the questionnaire. Corresponding to this result was the finding that the fans in the air handling units (AHUs) only operated when the thermostats demanded heating or cooling. Dry bulb temperatures in the credit union building on October 21 ranged from 72 to 78 °F, but averaged 75 °F [standard deviation (s.d.) = 1.5] throughout the day. Relative humidity levels ranged from 44 to 51% and averaged 48% (s.d. = 2.0) throughout the day. Carbon dioxide concentrations, however, ranged from 475 to 550 parts per million (ppm) and averaged 542 ppm (s.d. = 93.5) in the early morning; but climbed to between 1125 and 1725 ppm and averaged 1600 ppm (s.d. = 200.0) by the end of the day. A peak of 1800 ppm was measured at one location in the early afternoon round of measurements. During inspection of the HVAC systems, the AHUs were found to lack a means for providing outside air to ventilate the building. This finding, along with the thermostats being set to operate the AHUs’ fans only on demand for heating or cooling, is believed to have caused poor air circulation throughout the building. The original design of the HVAC system was further believed to have caused thermal comfort problems reported by many employees. Inspection of the HVAC system also showed that the units had additional problems that could have caused bioaerosol generation inside the units that could be blown into the building. Findings from the survey at the Sterling Van Dyke Credit Union are believed to show that deficiencies in the HVAC systems cause employee complaints. Contaminants such as ETS, bioaerosols, and sewer gases may also cause employee complaints and contribute to employees’ symptoms. The operation and design of these systems are also believed to cause employee thermal discomfort. Keywords: SIC CODE: 6062 (Credit Unions, Not Federally Chartered), indoor environmental quality, dry bulb temperature, relative humidity, carbon dioxide, environmental tobacco smoke (ETS), bioaerosols, thermal comfort, ventilation, air handling units (AHUs), maintenance. II. INTRODUCTION On September 24, 1993, the National Institute for Occupational Safety and Health (NIOSH) received a confidential request for a health hazard evaluation (HHE) at the Sterling Van Dyke Credit Union in Sterling Heights, Michigan from employees of the credit union. These employees were concerned about recurring illnesses. Symptoms and illnesses reported by the employees included headaches, backaches, breathing difficulty, asthma, and bronchitis. Purple fingernail beds and disrupted menstrual cycles were also mentioned as symptoms; but these symptoms are not commonly associated with building illnesses. One requester also indicated that at least four employees were using bronchial dilator inhalers. At least one of these employees was confirmed to have asthma by a pulmonologist; the others were thought, but not confirmed, to have asthma. III. BACKGROUND AND DESCRIPTIVE INFORMATION The Sterling Van Dyke Credit Union building is located in a fairly well- developed suburb of Detroit across the street from a Ford plant. The credit union is on the east side of and faces the street, which is a moderately busy four lane road. The credit union serves the Ford employees. The 4,675 square foot (ft2) (gross area) credit union is a single-story block and brick building on slab. The building was built in 1964. Most of the front of the building is floor-to-ceiling glass. Four, equally spaced, 2-foot wide floor-to- ceiling glass windows are in the north wall of the building, while four other smaller windows are in the west wall of the building. A layout of the building is shown in Figure 1. Two counter-flow air handling units (AHUs), AHUs 1 and 2, service the building. The AHUs contain gas-fired heat exchangers and freon cooling coils. Air is supplied to the building through a subslab distribution system. Most of the supply air fixtures for the building are 3" x 24" floor registers: eleven are located under all of the windows; two in Office 4 in Figure 1; and one in Office 5. The other supply diffusers are 4" x 12" low side-wall registers in each of the two bathrooms, two 4" x 12" high sidewall registers in Office 2, two 2" x 12" high sidewall registers in Office 1, and two 6" circular ceiling diffusers on the south side of the teller area. AHU 1 supplies air to the registers along the south, east and part of the north walls and the two ceiling diffusers. AHU 2 supplies air to the registers along the west wall, in the interior offices, and the remaining registers along the north wall. Locations for the diffusers are shown in Figure 1. Air returns to the AHUs through a ceiling plenum. Air enters the ceiling return plenum through four perforated metal grilles dispersed throughout the building, also shown in Figure 1. The return air in the ceiling plenum enters the return ducts through two parallel stub ducts that begin at the outer face of the mechanical room wall and run to each of the AHUs. No outside air is supplied to the AHUs, and no other mechanical system exists for supplying outside air to the building. Ventilation air can only enter the building through infiltration. Changes to the supply air distribution system since the original installation were the installation of the two registers on the interior wall of Office 1 in Figure 1, in place of one register on the exterior wall, and the addition of the two ceiling diffusers in the Teller Area. Each of the ceiling diffusers is connected to one of the ducts supplying the high sidewall registers in Office 2 with flexible ducting. Dates of the changes were unknown. In May 1992, new furnace sections of the AHUs were replaced because of cracks in the heat exchangers; the cooling coil sections of both units were not replaced. A defective condenser was replaced for one of the AHUs in June 1993.